Optical encoders use optical signals to detect mechanical positions and motions in various types of systems. The mechanical positions and motions detected by optical encoders can be related to linear or rotational displacements of moveable components, such as shafts of motors. There are two common types of optical encoders, absolute position encoders and incremental encoders. Both types of optical encoders can determine mechanical positions and motions. The absolute position encoders can determine the exact mechanical position at any moment of operation, even at power-up. The incremental encoders, on the other hand, lose the existing position data at power-down, and cannot determine the exact mechanical position at power-up. However, the incremental encoders are less expensive and require less processing power than the absolute position encoders. Thus, the incremental encoders enjoy a greater market share than the absolute position encoders.
A conventional optical encoder typically includes an encoder member positioned between a light source and a number of photodetectors. The encoder member includes a number of openings, which allow light from the light source to reach the photodetectors as the encoder member is rotated or linearly displaced with respect to the light source and the photodetectors. The photodetectors generate signals in response to incident light that can be analyzed to determine the relative speed or position of the encoder member with respect to the light source and the photodetectors.
A concern with the described conventional optical encoder is that the encoder member with the opening is relatively expensive to manufacture, which is reflected in the overall cost of the encoder.
In view of this concern, there is a need for a cost-effective optical encoder.